1. Field of the Invention
The invention relates generally to methods and devices for connecting tubing or pipelines, and more particularly to methods and devices for enabling sections of tubing or pipe to be connected when the sections are axially misaligned.
2. Description of the Related Art
Pipelines are commonly used to carry fluids under pressure. For the purposes of this disclosure, the words xe2x80x9cpipexe2x80x9d and xe2x80x9cpipelinexe2x80x9d are intended to include both the heavier tubular sections commonly referred to in the art as xe2x80x9cpipexe2x80x9d and the somewhat lighter tubular sections commonly referred to xe2x80x9ctubing.xe2x80x9dThe pipelines used in these applications typically consist of a number of pipe sections which are connected end-to-end to form a single conduit. In many cases, adjoining pipe sections are axially aligned so that they can be connected by means of standard flanges at the respective ends of the pipes which are bolted together.
A hammer union is one type of connector that is used to couple pipe sections together. One of the reasons that hammer unions are used is that they have fewer parts than bolted flanges and are easier to assemble. A hammer union generally comprises a first flange, a second flange and a hammer nut. The first and second flanges each have a sealing face and which is configured to form a seal when secured against the other""s sealing face. The hammer nut fits against the rear of the second flange to hold it against the first flange. The first flange is threaded to mate with a set of complementary threads on the hammer nut. Hammer unions may range in size from an inch or less to tens of inches in diameter.
The hammer nut typically has protrusions, or tangs, which can be hammered to twist the nut and thread it onto or off of the first flange. The aperture through the hammer nut may be small enough that the nut cannot fit over the second flange, or it may be large enough that the second flange can pass entirely through it. In the first instance, the nut must be placed on the pipe to which the second flange is connected from the end opposite the flange. Alternately, the flange may be placed on the pipe before the flange is connected to the pipe (e.g., by welding.) The nut is then moved along the pipe into contact with the flange so that it fits against the back of the flange. In the second instance, where the flange can fit through the aperture, slips are needed to retain the nut against the back of the second flange. The nut can be placed over the flange so that it is behind the flange""s rear surface, then the slips are inserted between the pipe and the nut. When the nut is moved forward against the second flange, the slips fits between the nut and flange so that the nut can hold the flange against a first flange.
In some cases, adjoining pipe sections and the flanges at the ends of the pipe sections may be misaligned. This may occur, for example, in marine environments, where it may not be possible to keep the pipe sections aligned when they are laid, or they may become misaligned due to environmental forces or repairs on the pipeline. The hammer nut in a hammer union, however, is normally designed to fit tightly against the back of the second flange and it cannot be threaded onto the first flange if the pipes and flanges are misaligned. This defeats the purpose of providing the hammer union, which is normally easier to assemble than a flange which has a set of bolts which have to be installed around its perimeter. Even if the nut of a hammer union could be threaded onto a misaligned flange, misalignment of the flange faces could prevent a proper seal from being made between them.
One or more of the problems outlined above may be solved by various embodiments of the connector disclosed herein. One embodiment comprises a hammer union for connecting pipe sections which may be either aligned or misaligned axially. The hammer union has a first flange, a second flange which mates with the first flange and a hammer nut (a retaining nut) which contacts the back of the second flange and is connected to the first flange to hold the flanges in place against each other. The back surface of the second flange and the inner surface of the retaining nut are complementary spherical surfaces which allow the nut to swivel with respect to the second flange. Therefore, when the first and second flanges are not axially aligned, the retaining nut can be swiveled to align with the first flange and can then be threaded onto the first flange.
In one embodiment, the first flange has a female mating surface and the second flange has a male mating surface. The mating surfaces are tapered (i.e., conical sections) and the male surface is tapered at a slightly greater angle than the female surface. A tapered sealing ring is placed between the male and female surfaces to provide a good seal, even when the mating surfaces of the two flanges are not completely aligned. The sealing ring is constructed of metal to enable it to withstand high pressures, high temperatures, dangerous fluids and other properties which may be found in industrial applications. The use of the tapered mating surfaces and the tapered sealing ring allow the flanges to provide a good seal even if there is some axial misalignment of the flanges. When the retaining nut is tightened, the forces on the flanges urge the flanges toward axially aligned positions.
In one embodiment, the retaining nut has tangs which extend outward from the body of the nut to facilitate the tightening or loosening of the nut. In smaller embodiments, this allows the nut to be more easily rotated by hand. In larger embodiments, the tangs allow the nut to be rotated by striking the tangs (e.g., with a hammer.) Slips or retainers may be used to allow the nut to be placed over the second flange and then held on the pipe section connected to the second flange. When slips are used, they provide the spherical retaining surface of the retaining nut.
In one embodiment, the male flange has a convex spherical mating surface and the seal ring has a complementary concave spherical inner surface. The male flange and the seal ring maintain contact and can provide a good seal while still allowing the male flange and the seal ring to swivel with respect to each other.